Frequently Asked Questions (FAQ)

Why ball drive?

Most of this question can be answered by the second question, which talks about advantages that ball drive has over other drive bases.

As to why we chose to build a ball drive: our team focuses on creating innovative and new robots, but not ones without merit. Ball drive is unconventional, but it also has definite advantages over other drive bases.

What advantages does ball drive have over a traditional holonomic, H, or swerve drive?

Ball drive combines simplicity and reliability with the maneuverability of mecanum or X-drive and the pushing power and traction of a tank or swerve drive. It also has the unique ability to have two different drive ratios with equal traction on each axis so one drive train can be both powerful and fast without using a transmission.

Here’s a few examples of advantages over other drivebases:

Simpler and more reliable than swerve drive or tank with a two-speed transmission

This depends on the task presented in Rover Ruckus, but we are hoping to use it in competition if possible! If not, we will be using it at outreach events and potentially in future seasons.

Is it completed?

Currently our first iteration of ball drive is completely designed and built, however it is still a work in progress and we may release improved versions in the future.

Are there any other examples of ball drive robots?

To our knowledge, our ball drive is the first to have four balls, however FRC team 45, the TechnoKats released a ball drive back in the 2003 FRC season that used two bowling balls on half of the drivetrain and omni wheels on the other half.

Where can I download/view a CAD model?

You can click here to view the complete CAD assembly in Fusion 360, and it can also be downloaded from there. Our CAD files are provided free and without license, however we ask that you give credit where it’s due and provide a link to this page in documentation.

How much does it weigh?

The drive base weighs 18 lbs in total, which includes electronics and a battery.

Why were custom balls used instead of off-the-shelf balls?

Off-the-shelf rubber balls of the precision we needed were not available for a reasonable cost. By custom-making our own balls we were able to reduce weight to less than 1 lb per ball while spending less on fabrication.

How were the balls made?

Here is a quick explanation. Our balls contain 3 inch foam cores that help keep weight and material costs low. We cast a ¼ inch layer of hard plastic around these cores, then cast an ⅛ inch layer of 70A hardness rubber to make a final ball with a 4 inch diameter. For more details on our manufacturing process feel free to contact us!

How reliable has ball drive been?

As a stress test, we took ball drive to our local Maker Faire, a two day/14 hour event. The drive base had no problems being driven for 7 hours a day on rough asphalt, and the only maintenance that was needed was tightening screws. We aren’t sure about reliability in competition environments yet, but the drive base seems to be very reliable mechanically.

How complex is the code that drives it?

Extraordinarily simple. Ball drive’s three motors are configured as two motors in a standard tank drive (one of the easiest drives to code), with an third motor which strafes exactly perpendicular to the tank drive. It requires none of the complex trigonometry of most holonomic drives. Your drive code can be only this: